1. Field of the Invention
The present invention relates generally to a hypodermic syringe and, more particularly, to a safety hypodermic syringe, which enables the plunger to be automatically disconnected from the stopper after the service of the syringe, leaving the stopper and the needle assembly inside the barrel.
2. Description of the Related Art
When disposing of a disposable hypodermic syringe after its service, the person handling the disposable hypodermic syringe may be injured by the protruding needle cannula accidentally. In order to eliminate this problem, safety hypodermic syringes are developed. These safety hypodermic syringes enable the needle assembly to be pulled backwards with the plunger and received inside the barrel after the service. Exemplars of these safety hypodermic syringes are seen in Taiwan Patent Application Nos. 189436; 356013; 463639; 414085; 384709; 359621; 492328; 467752; 475449; 480185; 497976; 430565; 471322; 332433; 394027; and 447310, and U.S. Pat. Nos. 5,385,557; 4,747,830; 4,677,980; 5,242,400; 4,986,813; 4,947,863; 5,533,975; 5,171,300; 4,944,723, . . . etc. These safety hypodermic syringes still have drawbacks. When the needle assembly received inside the barrel after the service of the hypodermic syringe, the plunger is still maintained secured to the stopper and the barrel. If the person disposing of the hypodermic syringe pushes the plunger accidentally, the needle cannula may be forced out of the barrel to injure the person disposing of the hypodermic syringe or a nearby person. In order to eliminate this problem, safety hypodermic syringes with a disconnectable plunger are developed. FIG. 1 shows a safety hypodermic syringe according to the prior art. According to this design, the plunger 11 has a neck 111 near the front side. When the needle assembly 13 and the stopper 12 received inside the barrel 14 upon a return stroke of the plunger 11, the user can twist the plunger 11 to break the neck 111. U.S. Pat. No. 4,944,723 shows a similar design. FIG. 2 shows a safety hypodermic syringe according to Taiwan Patent Publication NO. 492328. According to this design, a breaking groove 112 is provided in the connecting area between the plunger 11 and the stopper 12. When the needle assembly 13 and the stopper 12 received inside the barrel 14 upon a return stroke of the plunger 11, the user can disconnect the plunger 11 from the stopper 12 by biasing the plunger 11. U.S. Pat. No. 5,242,400 shows a similar design. FIG. 3 shows a safety hypodermic syringe according to Taiwan Patent Publication No. 378541. According to this design, the stopper 12 has a T-block 121 invertedly suspended at the bottom side, and the plunger 11 has a front coupling hole 113 detachably coupled to the T-block 121. When disconnecting the plunger 11 from the stopper 12, the user must twist the plunger 11 with force.
The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a safety hypodermic syringe, which enables the plunger to be automatically disconnected from the stopper after the service of the syringe, leaving the stopper and the needle assembly inside the barrel.
To achieve this and other object of the present invention, the safety hypodermic syringe comprises a barrel, the barrel comprising a body and a socket at a front side of the body; a needle assembly, the needle assembly comprising a needle hub mounted in the front socket of the barrel, the needle hub having a bottom retaining hole, and a needle cannula forwardly extended from the needle hub outside the barrel; and a plunger and stopper unit, the plunger and stopper unit comprising a stopper fitted into the body of the barrel, and an elongated plunger adapted to reciprocate the stopper in the body of the barrel, the stopper having an arrowhead-like front hook engageable into a bottom retaining hole of the needle hub for enabling the needle assembly to be pulled backwards with the plunger and stopper unit and received inside the body of the barrel; wherein the barrel has a stop device in a rear side of the body and adapted to stop the stopper from falling out of the body; the plunger comprises a plurality of equiangularly spaced and radially extended springy front wings, the front wings each having a crevice longitudinally extended to a front side thereof, the front wings including two opposite front wings, the opposite front wings each having a plurality of retaining blocks; the stopper has a plurality of locating blocks protruded from a bottom sidewall thereof and defining a receiving space adapted to receive the front wings of the plunger, the locating blocks each having a protruded engagement portion adapted to engage the retaining blocks of the opposite front wings of the plunger and to secure the plunger to said stopper. dr
FIG. 1 is a sectional side view of a safety hypodermic syringe according to the prior art.
FIG. 2 is a sectional side view of another design of safety hypodermic syringe according to the prior art.
FIG. 3 is a sectional side view of still another design of safety hypodermic syringe according to the prior art.
FIG. 4 is an exploded view of a safety hypodermic syringe according to the present invention.
FIG. 5 is an exploded view of the plunger and stopper unit of the safety hypodermic syringe according to the present invention.
FIG. 6 is a bottom view of the stopper of the plunger and stopper unit of the safety hypodermic syringe according to the present invention.
FIG. 7 is a schematic side view of the plunger and stopper unit of the safety hypodermic syringe according to the present invention, showing the front wings compressed and inserted into the crossed receiving space in the bottom side of the stopper.
FIG. 8 is a schematic side view of the plunger and stopper unit of the safety hypodermic syringe according to the present invention, showing the plunger fastened to the stopper.
FIG. 9 is a schematic side view of the present invention, showing a status of use of the safety hypodermic syringe.
FIG. 10 is a sectional view taken along line 10xe2x80x9410 of FIG. 9.
FIG. 11 is similar to FIG. 10 but showing an alternate form of the stop device.
FIG. 12 is a schematic side view of the present invention, showing the return stroke of the plunger and stopper unit.
FIG. 13 is similar to FIG. 12 but showing the plunger disconnected from the stopper.